Insulating Concrete Formwork

Insulating concrete formwork (ICF) can offer a quick, cost-effective route to an energy-efficient home
by Build It
26th November 2012

With the vast number of building options now available – including the wealth of modern construction methods that have emerged on the market – it’s tough to decide on what is best for your new home.

One option all too often overlooked is insulating concrete formwork (ICF). Perhaps thanks to unimaginative building design in the past – often being likened to bland concrete boxes – ICF buildings come with a stigma attached. But in fact, the innovative ICF method lends itself to flexible designs that can create beautiful modern structures. Commonly used in America and mainland Europe, the UK is now beginning to embrace ICF – especially within the self-build sector.

What is it?

ICF is an insulated in-situ concrete system comprising hollow blocks or panels, usually made of polystyrene, and ready-mix concrete. The blocks are stacked and fastened together with metal or plastic connectors to create the walls of a building and are pumped full of concrete to form the structure. The polystyrene is used as a permanent part of the structure.

The blocks can be easily used in a variety of different configurations, including curved walls, arches, angles and, of course, window and door openings. There are a large number of proprietors in the UK, so you can easily find a system that’s right for you.

What are the benefits?

One of the main benefits of ICF is the ease and speed of construction. A small team of semi-skilled (NVQ level 2) site operatives can put up the basic structure in a matter of days, saving time and money on labour.

Typically, a four-room ground floor can be erected in just a couple of days. This means that the exterior wall, insulation and structure are completed in just one process, saving money on any additional insulation that would otherwise be required. As for the exterior, almost any cladding system can be adapted to fit an ICF wall, so you don’t have to compromise on the final look of your house – it can be anything from a sleek modernist house to traditional cottage.

Another way ICF saves time on site is that it’s watertight as soon as the shell is up, so the follow-on trades can enter the building and start putting utilities and finishes into place much quicker than with traditional building methods.

What’s more, as well as being inherently strong, thanks to the concrete, it also has a high level of insulation thanks to the polystyrene, fantastic energy efficiency and a low U-value – which reach as low as 0.11W/m2K – saving money in the long term.

Another benefit, and a big plus in this age of environmental awareness, is that the system only produces a tiny amount of waste in construction. Any offcuts of polystyrene can be re-used elsewhere, on or off the build, and you can order the ready-mixed concrete to exact volume requirements.

Any disadvantages?

There are a couple of cons to building with this method, mainly the fact that adapting the house in the future – adding or moving doors and windows, or other utilities – can prove rather tricky and will require specialist cutting tools and advice from ICF experts, which will come at a price. This should not be too much of a problem for self-builders, who design to their own exact specification, unless you are definitely planning to remodel in the future.

There are also some cost implications. Initially an ICF home will come in at around 5 per cent more than the average timber-frame home. However, the money saved on construction time together with the energy savings you will make can offset this problem.

Case study: Logix UK

After perusing many self-build shows, Tim and Tracey Hawkins decided that they wanted to build their dream home with ICF, as the system would provide them with an energy-efficient dwelling quick to erect. Tim was interested in doing a training course on how to use the product and start the building work himself.

The Hawkins chose a system from Logix UK and found themselves a plot near Peterborough. But, as so often happens, problems arose in the planning stages. They discovered that the land had a restrictive covenant, in favour of the local estate – meaning that they needed approval from the local landowner who owned the majority of the land.

When Tim and Tracey met the landowner, they were told that the home had to fit architecturally with the traditional properties of the rest of the village. This wasn’t a problem, since the couple had decided beforehand that they wanted a rather traditional home and knew that they could clad the Logix system however they wanted.

The Hawkins were afraid that this year’s wet British summer would significantly delay the build, but as ICF systems are mostly immune to the rain, building works could in fact commence regardless of the weather. Within just two weeks the ground-floor structure and triple garage were erected and ready to be poured with concrete. Once this was done, the floor joists were fitted and the second storey went up just as quickly.

“Although you’re told that this build method is faster than more conventional ones, you don’t actually believe it until you see it with your own eyes or put it together with your own two hands,” says Tim.

The exterior of the home was finished off with Clipsham Gold limestone from Stamford Stone, which was quarried by a neighbour and rendered into building stone less than a mile away from the house.

Case study: Polarwall

The Haynes family work in the property industry, and when they decided to build their own home they knew exactly what they wanted and when they wanted it. The couple had a large plot in the countryside in Somerset and wanted to build an energy efficient home on it, quickly and cost effectively.

The Haynes chose to build their large modern home with an ICF system, Polarwall X50. The system provides an excellent U-value of 0.18W/(m2K), and with cladding, the home would be even better insulated. The house was built on a strip foundation with external Polarwall X50 walls. It was then clad in a combination of acrylic render, randomly set stone and horizontal cedar clapboard.

Polarwall trained the development company’s in-house builders in the formwork build techniques in under a week. Though none of the team had any previous experience of working with ICF, the finished walls were of an very high standard and the build team was satisfied with their first attempt at working with the new material.

The project manager commented: “All of us were very surprised by the robustness of the Polarwall formwork and the way it holds the weight of the fluid concrete, but what really impressed us was the straightness of the walls that we built. It is not at all difficult to work with, and it gave us a top-quality build rounded off with an excellent finish”.

The resulting house boasts clean architectural lines and a bold modern exterior. It is very well insulated, and the entire build programme took just six weeks.

Main image: This elegant self build was achieved using Beco Wallform’s ICF system

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